Hot cathode electron discharge tube



Sept. 2o, 1932.

H. M. FREEMAN ET AL HOT CATHODE ELECTRON DISCHARGE TUBE Original Filed Jan. 8, 1923 WITNESSES:

` 7 ATTORNEY Patented sept. 2o, 1932 UNITED STATE-s PATENT oFFlcEfl HUBERT M. FREEMAN, OF EAST `1?]2'1'IIISBURGrH, PENNSYLVANIArAND i WALLACEv G..

WADE, OF NEW YORK, N. Y., ASSIGNORS TO WESTINGHOUSE ELECTRIC' AND MANU- FACTURING COMPANY, A CORPORATION OF PENNSYLVANIA nor cAfrHonn Ennc'rnoiv nrscHARGEmUBE oi'ginaiappneation mea tem-Lary s,`1923, serial No.. 611,263;l Divided and this application inea uiye,

. 1926. serial No. 120,582. v

YThe: invention relates to hot cathode elec tron.discharge tubes and it has particular relation to grid-controlled tubes in which 3 the electron emitting cathode isy so heated from a source of alternating or, in general, fluctuating current as to substantially eliminate the undesirable effects ofthe variations of the heating current upon the electron-flow in the tube;

Various cathode structures :adapted for' that purpose have been disclosed in Your copending application Serial No. 611,263, filed J an. 8, 1923, ofl which the present application is 'a division.

p Among the objects of the jinvention .is an improved construction of an efficient cathode having the above-mentionedv characteristics' which maybe readily manufactured and which gives a particularly high degree ofV elimir'laytionv of the undesirable controlling ep'iiiects ofthe alternating heating current on the electron flow in the tube. f

In the preferred form of the invention, a iiat ribbon of tungsten is kdoubled to yform e a U-shaped heating member having a pair of adjacently positioned side sections. A thinsheet of micaor other suitable refractory insulating material, is'placed 'between the two sides of the U-shaped strip and serves to insulate the same from each other. cathode lelement' proper is constituted by strips of nickel placed onboth sidesl of the Ushaped tungsten stripv and insulated therefromby mica-sheet pieces, Orrin any other suitable fm'anner.' The outer surface of the...

The

eliminating the undesirable magnetic control of the electron flow in the tube.

The invention will be best understood from` the accompanying drawing, in which l Figure 1 is an enlarged sectional viewof an electron discharge tube, combinedwith a diagrammatic view of-'the associated cir- Y cuits', embodying the invent-ion, and Y Fig. 2 is an enlargedperspective view of, the to portion of the cathodestructurefutr lized m the tube shown in Fig. 1.

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Referring to the drawing, va radio-receiv- Y ing tube of a familiartype is shown l'comprising an elongated envelope 1 of glass or similar material, having a re-,entrant'stem 2. terminating in a press 3 in which are welded live lead-in wires 1 to 8, which serve to support, and to provide connections to,l a cathode memberlO, a grid 12 and a'plate 13 arranged concentrically, in the usualway.

rIhe cathode member 10, to which this vention particularly relates, comprises a heaterelement in the form of a U-shaped strip or ribbon 15 of tungsten or other suite' able material. rIhe ribbon is Vpreferably of-v flat cross section andl isdoubled uponA itself, the two sides 16 ofthe ribbon being insulated from each other to preventshort-circuits 'between the same. This maybe done by inserting a thinstrip or sheet 17 of mica, `or other suitable insulating material capable of withstanding the temperatures at which the' heating elementoperates, between the two,

flat sides of the U-shaped ribbon heater v15.' The cathode element proper is constituted by two flat sheets of conducting material 18,

such as nickel, assembled on both sides of the ribbon .heater 15, the4 outer cathode surface sheets being insulated from the adjacent ribbon sides 16 like the two sides v16 of the U-shaped ribbon element, for instance, by mica sheets 19 placed therebetween.l i' Theouter surface of the cathode sheets 18 are, of course, treated to have high electron' emission, for instance by coating theV same with oxides of barium, strontium and Vthe like. f y ,Theseveral sheet or strip members so assembled are suitably held together', for instance, by collar members 21, which tightly embrace the several elements at the upper and lower ends, respectively, thus uniting the same into a compact structure.

rIhe cathode member 10, so obtained, is supported at its upper end by means of a bail extension 22 secured to the upper collar 2l and welded, or otherwise securecL to a carrier `rod 23, which extends from lead-in wire Ll. rIhe bail connection between the upper collar 2l and the carrier rod 23 may also S-S1`Ve as the electrical lead to the active surface 18 of the cathode element and, in such case, the lead-in connection 4; to the carrier rod 23 may serve as a terminal of the cathode element.

At its lower end, the cathode member is supported through the connections of the ends of the U-shaped heater ribbon 15 to the lead-in wires 5 and 6 which serve to convey vthereto the heating current. When utilizing an electron tube as described above, the cathode is heated from a source of alternating-current, such as a transformer 25, the other connections to the tube being made in the usual way. Thuis, for instance, the input leads 26 of the circuit may be connected between the grid and cathode terminals 7 and 5, respectively, while the output leads 27 may be connected between the plate terminal 84 and the cathode terminal 4, respectively. Y

A cathode structure of the type described above, wherein a flat heater ribbon is used asa heating element, permits the construction of a very compact cathode, in which the magnetic fields induced by the alternating heating current are eliminated to a higher degree than is possible with-the other available constructions. It is, of course, understood that many other constructions embodythe ideasgdisclosed hereinabove will suggest themselves yto those skilled in the art, and the appended claims are intended to cover all such constructions.

VVeclaim as our invention:

l. In allot-cathode electron discharge tube, a cathode member comprising a V -shaped flat ribbon heater element having adjacently disposed'sides and a fiat sheet element of conducting material disposed adjacent to the surface of said heater element and separated therefrom by a layer of insulating material.

2. In an electron discharge tube, a cathode member comprising an even member of conducting ribbon heater elements Idisp osed with the fiat sides adjacent to each other, conducting sheet elements adjacent the outer sides of said adjacently-disposed heater elements, the adjacent surfaces of said heater elements and outer sheet elements being insulated from` each other, and the outer surfaces of said outer sheet elements being electron-emissive.

3. In an electron discharge tube, a cathode 1,e77,see

member having a heater element comprising an even number of longitudinal sheet elements having the flat sides disposed adjacent to each other, electron-emitting cathode elements disposed adjacent the outer surfaces of said sheet elements, the cathode elements being insulated from the adjacent surfaces of the heater element.

4. In an electron discharge tube having a heater element comprising an even number :K5 of sheet elements disposed with the {iat-sides opposite each other, electron-emitting sheet elements disposed adjacent the outer surfaces of said first-mentioned sheet elements, the individual sheet elements being insulated from each other by layers of refractory insulating material interposed between the-adjacent surfaces thereof( Y 5. In an electron discharge tube, a cathode member comprising a U-shaped ribbon heater element having adj acently disposed fiat sides, conducting sheet elements disposed adjacent the outer surface of said heater element', and having electron emitting outer surface portions, and layers of insulating material interposed between the adjacent surfaces of the several elements. v

6. In an electron discharge tube, U- shaped flat ribbon element having adj acently disposed fiat sides adaptedto be heated by sending current therethrough, and electronemitting surface means adjacent to the surface of said ribbon element and insulated therefrom, and means for providing individual terminal connections to said heater rib- @00 bon and said cathode element respectively.

7. Inan electron-discharge tube, a cathode structure having a heater element comprising a pair of serially-connected ribbon sections disposed with their flat sides facing each 105 other, and electron-emitting sheet elements having flat sides facing the outer surfaces of said ribbon sections, the several facing surfaces being electrically insulated, but having a relatively good heat-conducting connec- 110 tion.

3. In an electron discharge tube, a cathode structure comprising a pair of parallel-disposed, serially-connected heater ribbons having the fiat sides facing each other, electron 11" emitting conducting sheet elements disposed adjacent the outer sides of said ribbon elements, and insulating sheet elements interposed between the surfaces of said elements that face each other.

9. In an electron discharge tube, a cathode structure comprising a pair of parallel-clisposed serially-connected heater ribbons having their flat sides facing each other, electron-emitting'conducting sheet elements dis- 125 posed adj acent the outer sides of said ribbon elements, the adjacent facing surfaces 'being' separated from each other by sheets of mica.

10. In an electron-discharge tube,- a cathode structure comprising a pair of parallel-` L3@ Sil disposed7 serially-connected conductors at least one of Whiohis a heater ribbon having its flat side facing the other said Conductor, an electron-emitting surface adjacent Jhe outer side of said ribbon element, the adjacent tively.

HUBERT M. FREEMAN. WALLACE WADE. 

